Copying the theme and source code of https://pages.github.com/

I really like how https://pages.github.com/ has been implemented. In particular, I like how specific content is shown/hidden based on the user's selections. The fade-in effect is a nice touch too.

I'd like to create a tutorial for my own project with a similar look-and-feel (to be hosted on GitHub Pages). I can see that https://pages.github.com/ was built with Jekyll, using just one CSS file and one custom JS script + jQuery.